The objective of the proposed investigation is to carry out a detailed biochemical and immunological study of the type-common envelope glycoprotein D of herpes simplex virus (HSV) type l (oral form) and HSV-2 (genital form). Many structural and immunological properties of gD indicate that it is an important candidate for consideration as a subunit vaccine. We plan to localize, construct and characterize antigenic determinants of gD. We will characterize monoclonal antibodies from a number of laboratories in an effort to identify additional gD epitopes. Antibodies will be tested against a variety of fragments derived from gD, to facilitate mapping. In addition, synthetic peptides corresponding to the probable locations of specific epitopes will be synthesized and tested for antigenicity production of neutralizing antibody, and ability to stimulate a protective immune response in mice. Monoclonal antibody resistant (mar) mutants will be analyzed in an effort to further localize gD epitopes. Experiments are proposed to determine the number and location of disulfide bridges in gD-l and gD-2. These studies will be of importance in understanding aspects of the secondary and tertiary structure of gD. These structural studies will enable us to understand the nature of conformational epitopes. Preparations of gD-l and gD-2 and fragments derived from these proteins will be evaluated for their protective capacity in a mouse virus challenge model system. We will assess the relationship between stimulation of neutralizing antibody and protection against lethal virus challenge. The studies proposed in this grant will permit an assessment to be made of the usefulness of glycoprotein D or a derivative of it in stimulating a protective immune response.